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<br />Table 2 -Typical Range of Effective Friction Angle for Soils Other than Clays <br />• <br />Effective Friction Angle. (dee) <br />Soil Lose Dense <br /> <br />Gravel, crushed 36-40 40-50 <br />Gravel, bank run 34-38 38-42 <br />Sand, crushed (angular) 32-36 35-45 <br />Sand, bank run (subangular) 30-34 34-40 <br />Sand, beach (well-rounded) 28-32 32-38 <br />Silty Sand 25-35 30-35 <br />(After Bowles, 1979) <br />• With typical internal angles of friction of this material in the range of 34 to 42 degrees, a safe and <br />stable condition would exist at a slope angle of 2:1 V. <br />Generally, detailed slope stability analysis is required of any mine reclaimed fill slopes or operation <br />cut slopes if there is any doubt that the slope will be stable. In these analyses, it must be <br />demonstrated that the long-term slope safety factor (which is the ratio of resisting forces to driving <br />forces) be 1.3 or higher. Assuming a cohesionless soil (conservative), the factor of safety is equal to: <br />FS = ~ <br />Tan / <br />where: <br />~ =internal angle of friction <br />1=actual slope angle <br />• <br />Carol Ann Permit CDMG Application 7 8 <br />